Sound-generating apparatus



Sept. 10, 1929. T. LINDENBERG v SOUND GENERATING APPARATUS Filed Sept. 28. 1927 mental Sepe 1o, 192e.

UNITED STATES PATENT OFFICE.

SOUNDGENEBATING APPARATUS.

Application led September 28, 1927. Serial No. 222,639.

This invention relatesto improvements in sound generating apparatus and more par-I there being an adjustable tensioning device carried in connection with said frame for placing said diaphragm under the desired degree o tension necessary to procure its most eiiective operation, the said tensioning device being adapted to carry an electrical unit 2o formed to include a ieldexcited armature pivotall movable in response to the fluctuating e d created by said unit, said armature being connected at one end with a stylus which is also connected with the diaphragm, in order that the electrically induced movements of the armature will be mechanically imparted to the diaphragm and the latter thereby vibrated to produce corresponding audible sound waves. v

Among the objects of the invention are, to

mount t e electrical unit on the tensioning device so that as the latter is moved to place the diaphragm under more or less tension the electrical unit, including the armature and the stylus will be maintained constantly in predetermined and fixed ph sical relation to the diaphragm, avoiding the placing of these elements under undesired conditions of stress and strains or to avoid unnatural distortion thereof in their operative movements;

in providing an improved adjustable connection between the stylus and the diaphragm so that the pulsating movements imparted to the diaphragm by the movable stylus will be received over a comparatively wide area of the diaphragm to avoid fatiguing unduly the material of the diaphragmimmediately adj a cent to the point of connection with the stylus; rovidingior the convenient adjustment o the stylus and the associated armature of the field unit so that said armature will be properly spaced between the opposite poles of said unit and also prevented, when responding to strong field excitation or influences, from physically striking the frame structure of said unit and thereby creating objectionable sound disturbances; and in' the provision of' other improvements which will be hereinafter specifically set forth in the following description.

With these and other objects in view, as will appear as the description proceeds, the invention consists in the novel features of construction, combinations of elements and arrangements of parts hereinafter to be fully described and pointed out the appended claims.

In the accompanying drawing:

Figure 1 is a front elevation of the improved sound generating apparatus comprising the present invention,

Figure 2 is a rear elevation thereof,

Figure 3 is a vertical transverse sectional view on the line 3 3 of Figure 1,

Figure 4 is a transverse horizontal section al view on the line 4 4 of Figure l, and

Figure 5 is a detail horizontal sectional view disclosing Ion an enlarged scale the relationship between the electrical unit, the tensionlng frame, the diaphragm and associated parts.

Referring more particularly to the drawing my improved sound generating apparatus has been designated in its entirety by the nu'meral 1. This apparatus, in the specific embodiment of the invention illustrated, consists of 'a main-supporting frame 2 of substantially rectangular construction and formed from any suitable material. Across one face of this frame there is stretched a diaphragm 3 which, in this particular form of the invention, consists of a strip of leather, heavy paper or other material, andmay vary considerably in thick ness from that of relatively thin paper, to thick heavy leather, depending upon the character, pitch or qualit of sound which is desired to be created. n this instance thcl upper and lower edges of the diaphragm 'are secured to the frame 2 by means of fastening elements 4, which are threaded into the frame and their outer and headed threaded ends engaged with strips 5, which frictionally bear upon the end of the diaphragm 3 so as to securely clamp the latter in connection with the frame, this clamping is done, however, in such manner that normally the diaphragm will be loosely supported between its ends with a certain degree of fiex and fullness, as indicated more particularly in Figure 3.

In order to tautly stretch the diaphragm, however, I employ a tensioning devicewhich may consist of a pair of parallel bars 6, connected by vertically extending metallic straps 7, which have their opposite ends secured rigidly to the bars 6 in any suitable manner. The bars 6 are provided with beaded portions 8, which press against the inner surface of the diaphragm so as to force or stretch the latter upwardly. The necessary pressure is secured inattaining this object by the provision of a plurality of adjustable screws 9, which are carried the upper and lower b frame pieces of the fiiame 2. Manifestly by rotating the screws 9 the tensioning device may be moved outwardly against the diaphragm 3 and any suitable pressureapplied to the latter so as to place the diaphragmvunder the desired degree of operating tension. Of course, other suitable means may be employed for' securing this result, and I therefore do not desire to be limited to the construction herein selected for illustration.

Connecting the straps 7 of the tensioning device is a metallic disk 10, upon which is mounted an electrical unit l1 capable of creating a fluctuating electrical field. Units of this character are of standard construction A.and are found largelydn sound creating apparatus used'in connection with radio appliances. In this instance, however, the unit comprises a substantially U shaped core 12 suitably wound to create the electrical field. Within the core there is mounted a pivotally movable armature 13, which is adapted to oscillate, as usual, in accordance with the varying electrical pulsations effected through the energizing of the units 11.

To one end of this armature there is connected a stylus 14, which is provided with a relatively heavy threaded shank 15, the latter being receivable within openings formed centrally in the diaphragm 3 and within a revistering opening provided in a metallic washer 16. This washer, as shown in Figure 4, is of convex form, and is maintained in clamped engagement with the corresponding surface of the diaphragm 3 through the medium of adjustable threaded nuts 17 carried by the outer end of the shank 15. By medium of this construction it will be seen that by adjusting the position of the nuts upon the Shanks 15 the washer 16 will be securely fas'- tened in an applied position upon the outer surface of the diaphragm 3 so as to receive the thrust imparted thereto by the reciproeating stylus, enablinv the ceive the pulsations o? the stylus over a comparatively large'area, so as to avoid unduly fatiguing that portion of the diaphragm to which the stylus is immediately connected. Moreover, another important advantage is obtained in that through the medium ofthe adjustment set forth the operating position of the armature 13 may be carefully regulated by an extraneous adjustment. This enables the armature to be centrally positioned between the opposite sides of the core 12,

preventing the armature, when responding to strong field excitations, from contacting with the metal frame of the electrical unit, and thereby setting up objectionable sound disturbances.

In View of the foregoing it will be seen that the present invention provides a simple and improved sound creating agency wherein provision is made, by the mountingof the electricalunit on the tensioning frame, to maintain at all times a fixed relationship between the electrical unit and the diaphragm, so that regardlessly -of the degree of adjustment of said diaphragm there will be maintained a constant distance between the'armature and the central portion of the diaphragm, preventing the placing of unnatural stresses and strains on the stylus and armature connections. Again, provision is made for distributing the thrusts and pull of the stylus over a considerable area of the diaphragm, to avoid excessive strain on that portion of the diaphragm to which the stylus is connected, and finally, the provision ofan exterior adjustment for carefully determining the operating positions of the pivoted armature.- These features, both singly and collectively, contribute toward the production of a sound creating apparatus for producing or generating sound free and; clear' from distortion and unnatural qualities and, conversely, the creation of sound of natural properties wherein harmonics and overtones are very clearly discernible.

What isv claimed is:

1. In a device of the character set forth, a base, a diaphragm connected with said base, a tensioning device comprising a frame formed to include a-pair of parallel bars engaging the diaphragm at a point near its connection to said base, adjustable tensioning means carried by said base for moving the tensionin device with said bars into engagement witli said diaphragm to maintain the latter in a taut vibratory condition, an electrical unit supported by and movable in unison with said tensioning device, and a mechanical connector between said electrical unit and said diaphragm.

2. In a sound enerating device of the character described, a base, a diaphragm of tions thereof secured to said base, a tensiondiaphragm to reing frame situated within a recess formed in said base, adjustable means carried by said base for moving said tensioning frame within said recess into enga ement with said da- 5 phragm, said frame an diaphragm lying a't all times in a. parallel relationshi with each other, an electrical unit carried y said tensionin frame, and a stylus having an adjustab e connection with the center of said 10 dahragm.

' testimony whereof I ax m si ature.

THEODORE LINDE IRG. 

